[Python-Dev] PEP 215 redux: toward a simplified consensus? (original) (raw)

M.-A. Lemburg mal@lemburg.com
Mon, 25 Feb 2002 19:08:48 +0100

"Barry A. Warsaw" wrote:

Background: PEP 215 has some interesting ideas, but IMHO is more than I'm comfortable with. At IPC10, Guido described his rules for string interpolation as they would be if his time machine were more powerful. These follow some discussions we've had during various Zope sprints about making the rules simpler for non-programmers to understand. I've also been struggling with how error prone %(var)s substitutions can be in the thru-the-web Mailman strings where this is supported. Here's what I've come up with. Guido's rules for $-substitutions are really simple: 1. substitutes to just a single $ 2. $identifier followed by non-identifier characters gets interpolated with the value of the 'identifier' key in the substitution dictionary. 3. For handling cases where the identifier is followed by identifier characters that aren't part of the key, ${identfier} is equivalent to $identifier. And that's it. For the sake of discussion, forget about where the dictionary for string interpolation comes from.

Wouldn't it be a lot simpler and more inline with what we already have, if we'd use '%' as escape characters ?

  1. %% becomes %

  2. %ident maps to %(ident)s as we have it now

  3. %{ident} maps to %(ident)s

  4. %(ident)s continues to have the same semantics as before

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